Study: Plastics, Garbage Fuel Texas Cement Kiln

A recent study (PDF) from the American Chemistry Council and the University of Texas at Austin has demonstrated that fuel created from nonrecycled post-consumer plastics and other waste can be used to power energy-intensive commercial and industrial operations.

Michael Webber and his team of researchers at the University of Texas at Austin Cockrell School of Engineering tested a fuel made from nonrecycled residue from material recovery facilities (MRFs), which sort municipal waste. About 5 to 15 percent of that waste is too contaminated or soiled to be recycled economically, and it normally would go to landfills. This residue is composed mostly of high energy content nonrecycled plastics and fiber -- mostly paper, paperboard, and cardboard.

A study demonstrated that solid recovered fuel created from nonrecycled plastics and other wastecan power energy-intensive commercial and industrial operations.(Source: Balcones Resources/University of Texas at Austin)

This mixed residue can be processed into solid recovered fuel (SRF), which can replace or supplement traditional fuel sources. The study looked at the benefits and tradeoffs -- economic, energetic, and environmental -- of converting nonrecycled post-consumer plastics and fiber waste from MRF streams into SRF. A pilot project tested an SRF created from such residue and used to power a cement kiln in Texas.

Balcones Fuel Technology of Little Rock, Ark., used a blend of 60 percent MRF residue and 40 percent post-industrial waste products to produce a mix estimated at 60 percent plastic and 40 percent fibrous material. The research team conducted an experimental test burn of 130 tons of the fuel in the cement kiln's precalciner, a combustion chamber that preheats and decarbonizes raw materials before they enter the kiln. A ton of the fuel was fed into the kiln every hour for 24 hours. The rate was then raised to two tons per hour for the next 48 hours.

Based on heating value measured during the experiment, the SRF supplied about 10 percent of the precalciner's energy needs during the one-ton/hour test and 20 percent during the two-ton/hour test. The researchers also sent a sample of the fuel to an independent lab for elemental analysis and energy value calculation. The study found that the SRF provides the same energy (Btu/lb) as the bituminous coal the kiln normally uses. The SRF's energy density is 10 percent higher than sub-bituminous coals and 80 percent higher than lignite coals.

Researchers also recorded emission data from the test burn. The data was used in a lifecycle analysis of SRF production and use, including transportation, landfill, and processing steps. Energy use and emissions were tracked at each step for two cases. In the reference case, MRF residue went to a landfill, and the kiln used only coal for fuel. In the SRF case, the residue was processed into fuel and offset some of the coal used to power the kiln. The SRF case reduced the kiln's sulfur dioxide emissions by 50 percent and carbon emissions by 1.5 percent over the reference case. The lifecycle analysis showed that, at one ton/hour, the SRF reduced sulfur dioxide emissions by 19 percent to 44 percent.

Webber's study concluded that diverting as little as 5 percent of nonrecyclable materials from MRFs and recovering their energy in the form of SRFs would generate enough energy to power 700,000 American homes each year. By displacing coal, that diversion would eliminate the same amount of carbon emissions as removing a million cars from US roads.

Definitely an interesting idea to create fuel from non-recycled plastics. But while there are obvious energy benefits, what about the emissions and environmental/human safety factor? I, for one, am not a fan of breathing in what would seem to be plastic residue.

Beth, SRF is created by compression, not by burning. The emissions discussed here are from the normal operation of the cement kiln, not from creating the fuel. Cement kiln emissions were lower using this fuel than using coal.

The idea is to use a resource that's being wasted and would otherwise end up producing C02, plus get a cleaner-burning fuel. SRF is more common in Europe and other countries, but less so in the US, as we discuss herehttp://www.designnews.com/author.asp?section_id=1392&doc_id=242808

Thanks, Nadine. This is a different type of fuel than JBI makes. It's a solid recovered fuel (SRF) that mixes plastic and other waste, mostly paper-based, via compression into pellets that can be burned. As we reported herehttp://www.designnews.com/author.asp?section_id=1392&doc_id=242808JBI does something quite different: plastics to fuel (PTF) using pyrolysis (thermochemical, not burning), which creates fuel oil out of plastics via chemical, not mechanical, processes. Regarding commercialization, I don't think anything in particular is keeping these technologies from the market. They've all been in R&D for awhile and are in process of being scaled up. North America is considerably behind Europe in this field, partly because (I've been told) we've had more room for landfills so less motivation.

Thanks for the clarification on the different processes Ann. I was referring to the fact that both use post-consumer trash or recyclables to make fuel. I should have been clearer.

How is Europe ahead of North America using this? I haven't heard of any large-scale use of this type of fuel.

Most new or expanded landfills in the US are placed in extremely poor communities. I don't think we have the space. I think it's that marginalized areas are easily manipulated here. It's hard to focus on protecting the environment when the kids are hungry.

Nadine, to clarify, these do not use recyclables, but items that can't be recycled. To answer your question, during the reporting for this feature article on fuels from plastic: http://www.designnews.com/author.asp?section_id=1392&doc_id=242808 I learned from industry experts that solid recovery fuel (SRF) and/or refuse derived fuel (RDF) processes, which mix paper with plastic, are more common in Europe, but not yet so in North America. I also learned that, in general, because there's much less landfill space--due to much smaller geography and higher population density per square mile--Europe is farther along in R&D and also deployment of turning plastics into fuel, meaning prevalence, not scale of deployment.

The carbon emissons are only 1.5 % ? that is pitiful. This is probably within experimental error. why bother with this approach? Is SO2 that big an issue to scrub? I suggest it is misleading to take huge landfill numbers and mulitply by some small possible not even real % and claim that recovering energy from SRF s is equal to 700,000 homes /yr.

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